Field of the Invention
The invention relates to a power semiconductor module which includes a plastic housing, a plurality of connection elements for external main connections and control connections and at least one ceramic substrate. The at least one ceramic substrate has at least on its upper side a structured metalization, is fitted with semiconductor components and is inserted into a bottom opening of the plastic housing.
A power semiconductor module of this type is for example described in detail in Published, Non-Prosecuted German Patent Application No. DE 36 04 313 A1.
The ceramic substrates used in these power semiconductor modules usually are formed of aluminum oxide Al2O3 or AlN and are provided with solderable conductor tracks, i.e. a structured metalization.
In the case of the ceramic substrates, which are formed of aluminum oxide, these conductor tracks are produced by a direct copper bonding process, whereas, in the case of ceramic substrates, which are formed of aluminum nitride, the conductor tracks are produced by an active metal brazing process. Both processes have been extensively described in the prior art.
The load connections and control connections are butt-soldered onto the connection surfaces provided on these solderable conductor tracks, as metal angle-brackets, end wires or stamped-and-bent parts. To compensate for tensile and flexural loads which occur, compensating curves or arcs, for example, are provided in the load connections and the control connections. However, the joints produced in this way frequently have problems with regard to the mechanical reliability of the joints.
Furthermore, the use of load and control connections in combination with compensating curves requires a greater amount of space, and consequently restrictions are imposed on the miniaturization of the power semiconductor modules.
Connection tabs, which project beyond the outer edges of the ceramic substrates are generally welded or soldered to connection plugs or load connections.
It is accordingly an object of the invention to provide a power semiconductor module which overcomes the above-mentioned disadvantages of the heretofore-known power semiconductor modules of this general type and which ensures increased mechanical reliability in the joints of the load connections and/or the control connections to the ceramic substrate and, at the same time, takes up less space for the load and/or control connections.
With the foregoing and other objects in view there is provided, in accordance with the invention, a power semiconductor module, including:
a plastic housing having a bottom opening formed therein;
a plurality of connection elements for external main connections and control connections;
at least one ceramic substrate having an upper side and being inserted into the bottom opening of the plastic housing;
semiconductor components provided on the at least one ceramic substrate;
a structured metalization provided at least at the upper side of the at least one ceramic substrate, at least a part of the structured metalization being detached from the at least one ceramic substrate and being bent vertically upward for forming a grip tab; and
the grip tab being joined to one of the connection elements.
In other words, the object of the invention is achieved by a power semiconductor module of the type described in the introduction which is characterized in that at least a part of the structured metalization has been detached from the ceramic substrate and has been bent vertically upward to form a grip tab or holding tongue, and in that the grip tab is joined to a connection element for external connections or terminals.
In this procedure, parts of the metalization are detached from the metalization of the ceramic substrates at the required connection points and are bent vertically upward. The load and/or control connections, which lead to the outside are attached to these grip tabs which are formed within the ceramic substrates. The grip tabs are typically joined to the connection elements by a brazed (hard-soldered) joint or a welded joint, so that a significantly stronger and mechanically more reliable joint can be produced.
With the soft-soldered joints, which have hitherto been produced in the prior art, it was impossible to achieve a strength, which equals that of a brazed or a welded joint.
This measure allows a reliable, temperature-resistant joint to be produced between the metalization on the ceramic substrate and the connection element, and in particular no filler or additional material is required when forming the joint as a welded joint. Consequently, the mounting times can be reduced considerably.
Furthermore, these measures enable the power semiconductor modules to be miniaturized further, since there is no need for compensating curves or arcs in the load and/or control connections.
Furthermore, relatively short load connections with a large line cross section can be realized. Load connections of this type have a significantly lower electrical resistance than the load connections used in the prior art.
Finally, the measures according to the present invention mean that there are no insulation problems caused by parts of the ceramic substrates breaking off. The breaking of the ceramic substrates is caused by an excessive notch action below solid accumulations of material of connection elements in the event of thermal load changes.
Overall, the present invention enables power semiconductor modules, which are significantly more reliable than those used in the prior art and have smaller dimensions.
According to another feature of the invention, at least one ceramic substrate is an aluminum oxide substrate including Al2O3 or an aluminum nitride substrate including AlN.
According to yet another feature of the invention, the structured metalization is a copper metalization.
According to a further feature of the invention, the structured metalization has a surface; and a nickel layer is provided on the surface of the structured metalization.
According to another feature of the invention, the plastic housing includes a frame and a cover.
According to yet another feature of the invention, the cover has openings formed therein, and at least some of the connection elements are guided through the openings.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a power semiconductor module, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.